The application relates to geologic modeling, and in particular to the interactive creation of a computerized model of a geologic domain cut by multiple fault surfaces and geologic horizons.
Accurate modeling of a subsurface domain, such as a reservoir under investigation for possible petroleum content, or in more general terms a geologic basin, is critical to the ongoing investigation of that domain. Drilling exploratory wells is an expensive undertaking, as is a full-scale seismic or magnet survey, and accurate decision-making requires accurate geological mapping.
Information about the geologic horizons present in a reservoir is clearly an important first step. Knowledge of the type and thickness of sedimentary strata gives a geologist key information in visualizing the subsurface structure. In most areas, however, strata are cut with numerous faults, making the analytical task considerably more complicated. Geologic mapping requires that the faults be identified and that the amount of the slippage along the fault plane be quantified. The amount of slippage, or “throw”, can range from little to no actual movement nn the case have a fracture, to a distance of hundreds of kilometers along a major fault zone such as the San Andreas fault of California.
A 3-D model of a geologic domain would be a highly useful tool for geologists and exploration planning managers. That technology lies at the intersection between geology, geophysics, and 3-D computer graphics, and several inherent problems need to be overcome in such a product. First, data is often incomplete. The volumes in question range from the earth's surface down many thousands of feet, and data is generally difficult to obtain. Moreover, the data that is available, often in the nature of seismic survey results and well log data, is subject to considerable processing and interpretation. Second, a large measure of professional judgment goes into the rendering of any such analysis, so that the goal of any analytical tool cannot be a complete result, but rather should be aimed at assisting the geologist of to bring her judgment to bear in the most of efficient and effective manner possible.
A further difficulty stems from the inherent complexity of the problem. A typical petroleum reservoir, for example, will include a minimum of 20-50 fault surfaces up to a maximum of several hundred. A user could manually deal with a small number of fault surfaces, but this level of complexity is literally overwhelming. And not only is the task made more difficult by the sheer number of data points, but the data themselves are also highly complex. Fault structures can assume a number of shapes and configurations that are extremely difficult to depict and visualize.
The prior art offers several products, all of which fall short of an effective solution. For example, a computer program marketed under the name “Petrel”, provided by Schlumberger Limited, offers the capability of producing smoothed fault surfaces, but the system has difficulty dealing with complex fault structures. Another product, called Go-CAD, produced by Earth Decision Sciences, is similarly challenged by complex surfaces. Both of these products offer 3-D visualization tools, but those do not offer the user sufficient flexibility to produce a model that is ready for a geologist's interpretation.
Finally, Dynamic Graphics, Inc, of Alameda, Calif., offers a product called Earth Vision, which is aimed at this problem. That program works with a fault network, constructed on a binary tree, but that data structure is not presented in a way that users can adopt with high productivity, and it has difficulty dealing with vertical or near-vertical faults.
Thus, no product has emerged combining ease of use and the ability to deal with masses of complex data, coupled with the ability to produce a result ready for interpretation by a geologist. Those tasks remain unsolved in the prior art.